and `warn-nobacktrace` are the supported actions. The default is to `abort`,
which halts the machine. Some (but not all) operations also support continuing
execution with a "permission denied" error being returned to the program.
- `warn` prints a full backtrace when that happen; `warn-nobacktrace` is less
+ `warn` prints a full backtrace when that happens; `warn-nobacktrace` is less
verbose. `hide` hides the warning entirely.
* `-Zmiri-env-exclude=<var>` keeps the `var` environment variable isolated from the host so that it
cannot be accessed by the program. Can be used multiple times to exclude several variables. The
`-Zmiri-disable-isolation` is set.
* `-Zmiri-ignore-leaks` disables the memory leak checker, and also allows some
remaining threads to exist when the main thread exits.
+* `-Zmiri-permissive-provenance` disables the warning for integer-to-pointer casts and
+ [`ptr::from_exposed_addr`](https://doc.rust-lang.org/nightly/std/ptr/fn.from_exposed_addr.html).
+ This will necessarily miss some bugs as those operations are not efficiently and accurately
+ implementable in a sanitizer, but it will only miss bugs that concern memory/pointers which is
+ subject to these operations.
* `-Zmiri-preemption-rate` configures the probability that at the end of a basic block, the active
thread will be preempted. The default is `0.01` (i.e., 1%). Setting this to `0` disables
preemption.
provenance](https://github.com/rust-lang/rust/issues/95228) checking in Miri. This means that
casting an integer to a pointer yields a result with 'invalid' provenance, i.e., with provenance
that cannot be used for any memory access.
+* `-Zmiri-symbolic-alignment-check` makes the alignment check more strict. By default, alignment is
+ checked by casting the pointer to an integer, and making sure that is a multiple of the alignment.
+ This can lead to cases where a program passes the alignment check by pure chance, because things
+ "happened to be" sufficiently aligned -- there is no UB in this execution but there would be UB in
+ others. To avoid such cases, the symbolic alignment check only takes into account the requested
+ alignment of the relevant allocation, and the offset into that allocation. This avoids missing
+ such bugs, but it also incurs some false positives when the code does manual integer arithmetic to
+ ensure alignment. (The standard library `align_to` method works fine in both modes; under
+ symbolic alignment it only fills the middle slice when the allocation guarantees sufficient
+ alignment.)
The remaining flags are for advanced use only, and more likely to change or be removed.
Some of these are **unsound**, which means they can lead
application instead of raising an error within the context of Miri (and halting
execution). Note that code might not expect these operations to ever panic, so
this flag can lead to strange (mis)behavior.
-* `-Zmiri-permissive-provenance` disables the warning for integer-to-pointer casts and
- [`ptr::from_exposed_addr`](https://doc.rust-lang.org/nightly/std/ptr/fn.from_exposed_addr.html).
- This will necessarily miss some bugs as those operations are not efficiently and accurately
- implementable in a sanitizer, but it will only miss bugs that concern memory/pointers which is
- subject to these operations.
-* `-Zmiri-symbolic-alignment-check` makes the alignment check more strict. By
- default, alignment is checked by casting the pointer to an integer, and making
- sure that is a multiple of the alignment. This can lead to cases where a
- program passes the alignment check by pure chance, because things "happened to
- be" sufficiently aligned -- there is no UB in this execution but there would
- be UB in others. To avoid such cases, the symbolic alignment check only takes
- into account the requested alignment of the relevant allocation, and the
- offset into that allocation. This avoids missing such bugs, but it also
- incurs some false positives when the code does manual integer arithmetic to
- ensure alignment. (The standard library `align_to` method works fine in both
- modes; under symbolic alignment it only fills the middle slice when the
- allocation guarantees sufficient alignment.)
+* `-Zmiri-retag-fields` changes Stacked Borrows retagging to recurse into fields.
+ This means that references in fields of structs/enums/tuples/arrays/... are retagged,
+ and in particular, they are protected when passed as function arguments.
* `-Zmiri-track-alloc-id=<id1>,<id2>,...` shows a backtrace when the given allocations are
being allocated or freed. This helps in debugging memory leaks and
use after free bugs. Specifying this argument multiple times does not overwrite the previous
* `MIRI_TEST_TARGET` (recognized by the test suite) indicates which target
architecture to test against. `miri` and `cargo miri` accept the `--target`
flag for the same purpose.
+* `MIRI_NO_STD` (recognized by `cargo miri` and the test suite) makes sure that the target's
+ sysroot is built without libstd. This allows testing and running no_std programs.
* `MIRI_BLESS` (recognized by the test suite) overwrite all `stderr` and `stdout` files
instead of checking whether the output matches.
* `MIRI_SKIP_UI_CHECKS` (recognized by the test suite) don't check whether the
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